Google Now works by presenting you with a list of 'cards' containing relevant information that you want....the cards that I have chosen are my traffic to work, the weather and some sports scores.....you'll get a notification when something changes, but you can always go to the dashboard and look at the cards that way too.

I've been using Google Now since it was introduced months ago, and it is really awesome. It doesn't require you to ask it for information, it just proactively gives you the information you want.